This meant lots of "pinwheels" for customers visiting those sites. That's bad for business—for both the ecommerce sites and Facebook.

Facebook's current business—advertising—is decelerating, and so people who are buying the stock hope that someday, the company will figure out how to monetize its 900 million users. If Facebook doesn't prove to be a reliable partner to e-commerce sites, e-commerce will not be the solution.